docs: def setAnonymous(self, is_anonymous):
          """Set whether this request should be made anonymously. If a
          request is anonymous, the identifier will not be sent in the
          request. This is only useful if you are making another kind of
          request with an extension in this request.
  
          Anonymous requests are not allowed when the request is made
          with OpenID 1.
  
          @raises ValueError: when attempting to set an OpenID1 request
              as anonymous
          """
          if is_anonymous and self.message.isOpenID1():
              raise ValueError('OpenID 1 requests MUST include the '
                               'identifier in the request')
          else:
              self._anonymous = is_anonymous